Temporomandibular Joint And Occlusion Station Flashcards
What is the ICP?
Intercuspal position: maximum interdigitation (dependent on dentition to be reproducible)
Does your patient have a reproducible ICP?
Get patient to bite together a few times and gauge.
PDL mechanoreceptors aid sensing movement back into the same position, therefore dentate patients should have a reproducible ICP but the more teeth lost i.e. edentulous patients, the more likely the ICP is not reproducible.
How to identify suitable index teeth
When the patient is biting together which teeth clearly meet together in a reproducible way i.e upper 5, lower 4.
Fox’s guide plane
Device held to the maxillary arch to gauge the occlusal plane - important when making dentures i.e. can make adjustments where necessary.
What reference planes are used when using a Fox’s guide plane?
Interpupillary line
Ala-tragal line
How would you examine the contact of teeth for ICP and excursions?
Using articulating paper: patient bites down into ICP then slides the teeth to left and right.
What is RCP?
Retruded contact position
What is retruded contact position?
Condyle retruded in the glenoid fossa, teeth in contact but ~1-2mm posterior to ICP (can sometimes be the same as ICP)
How would you get your patient into RCP?
Curl tongue to the back of the mouth and bite together.
OVD
Occlusal vertical distance (height of the lower 1/3 of the face when in the ICP)
RVD
Resting vertical difference (height of lower 1/3 of face when in the resting postion)
FWS
Freeway space
How is the Freeway space determined?
- Looking at patient at rest
- Looking at patient speaking
- Two dots and measure
- Mirror handle and hand
- Willis gauge
Willis gauge
Used to gauge the freeway space
Set up of Willis gauge
Note: can check it’s set up correctly by checking it makes a “T” shape
How is the free way space calculated?
RVD - OVD = FWS
How to get a patient into the rest position?
Lick lips and swallow, gently close lips together.
What would a patient with a large freeway space look like?
Appear more ‘squished’ or ‘older’
Appearance of a patient with a very small FWS?
Much ‘longer’ lower 1/3 of face “horsey”.
What materials are available for recording occlusion?
- Dental impression gun (mixes the material inside)
- Pink wax (heat with warm water)
- Grey wax (harder)
Condylar movement: working side (side moving towards)
- Rotates around vertical axis
- Lateral bodily movement (Bennett movement)
Condylar movement: Non-working side (side jaw’s moving away from)
- Moves downwards/forwards over eminence
- Moves medially
This movement is the Bennett Angle
Does balances occlusion occur in natural teeth?
No (cannot exist in normal dentate occlusion)
Does balances occlusion occur in dentures?
It’s opted for to provide stability for full dentures. Basically means that as much teeth are in contact as possible —> can be difficult to achieve!
Why might freeway space be important when making dentures?
IT MUST BE ACCOUNTED FOR:
When the denture base has been raised inappropriately to the rest position; that is, with teeth contacting at this position, the result is that the mandibular musculature, especially the masseter, becomes severely stressed.
Occlusion can be guided by either…
- Canine guidance
- Group function
Why is it important to know how the occlusion is guided?
For selecting the correct articulator when making dentures (also can be important when doing restorative work).
What is the average FWS?
2-5mm
How would you estimate FWS in Edentulous patients?
RVD + 3 —> then adjust denture accordingly!
Describe the anatomy during: jaw opening
hinge movement with the condyle turning round an axis
Describe the anatomy during: wide jaw opening
hinge and slide movement of the condyle
Describe the anatomy during: wide jaw opening
hinge and slide movement of the condyle
Describe the anatomy during: protrusion
Sliding forwards of the condyle
TMJ: basic description
a synovial joint between temporal bone and mandible
Features of a synovial joint
Synovial fluid inside a synovial membrane attached by a joint capsule to two bones.
Hyaline articular cartilage covering each bone.
Joint capsule of the TMJ
Attached to the glenoid fossa.
2 layers: outer fibrous layer, inner synovial membrane.
What does the synovial membrane do?
Secretes synovial fluid to fill the space (proteoglycans, lubricant, nutritive).
Lateral ligament of TMJ
Part of the capsule.
Attaches: lateral surface of articular eminence - posterior surface of condyle
What role does the lateral ligament play?
Restricts posterior, lateral, inferior, contra lateral medial, and pure hinge movement.
What are the three accessory ligaments of the TMJ?
- Stylomandibular
- Sphenomandibular
- Pterygomandibular raphe
What are the 5 zones of the articular disc?
- Anterior extension
- Posterior extension
- Anterior band
- Intermediate zone
- Posterior band
In the posterior extension of the articular disc there is an upper and lower layer, what is different about these two layers?
Upper —> vascular and elastic
Lower —> fibrous
The anterior extension of the articular disc is continuous with the ____________.
superior head of the lateral pterygoid muscle.
Nerve supply to the TMJ
V3
- auriculotemporal
- masseteric
- deep temporal
TMJ blood supply
- superficial temporal artery
- maxillary
What should happen to the articular disc as the condyle moves?
It should move with it..
What is anterior disc displacement?
When the articular disc has moved anterior to the condyle.
WIT REDUCTION: means that as the condyle slides forwards during mouth opening there is a click and the disc snaps into place.
Superficial and deep Masseter: insertion and origin
Origin: zygomatic arch (superficial) and inner aspect of zygomatic arch (deep)
Insertion: angle/ramus of mandible (same for both)
Function of the masseter
Jaw elevation (closing)
Minor protrusive (superficial masseter only)
Innervation of masseter
Vc Motor root - masseteric nerve
Temporalis: origin and insertion
Origin: inferior temporal line and fascia
Insertion: coronoid process
Function of temporalis muscle
Jaw elevation and retrusion (posterior fibres)
Temporalis innervation
Vc motor root - deep temporal nerve
Lateral pterygoid (upper head) insertion and origin
Insertion: capsule and articular disc of TMJ
Origin: infratemporal surface of greater wing of sphenoid
Lateral pterygoid (lower head) insertion and origin
Origin: lateral aspect of lateral pterygoid plate
Insertion: pterygoid fovea below head of condyle
Is the lateral pterygoid a true jaw opener?
- Not involved during initial opening
- However, during wide opening the inferior lateral pterygoid (green) allows the movement of the condyle downwards and forwards (“slide”)
What are the three functions of the inferior head of the lateral pterygoid muscle
- protrusion (sticking out jaw forwards
- assists opening
- lateral excursions (unilateral pull of condyle forwards)
Lateral pterygoid (superior head) function
- Retrusion and closing
Medial pterygoid: insertion and origin
Origin: medial aspect of lateral pterygoid plate (deep head) and Maxillary tuberosity (superficial head)
Insertion: medial aspect of ramus/angle of mandible
Function of medial pterygoid muscle
- Jaw elevation
- Assists protrusion and lateral excursions (unilateral)
Innervation of medial pterygoid
Vc motor root - nerves to medial pterygoid
Genohyoid: origin and insertion
Origin: inferior mental spine & inferior genial tubercle
Insertion: hyoid bone
Geniohyoid function
Hyoid fixed: opening/retrusion of mandible
Hyoid not fixed: raise/forward hyoid bone
What nerve innervates the geniohyoid?
C1 (with hypoglossal)
Mylohyoid muscle attachments
originates from mylohyoid line on the mandible.
Inserts into itself at the median raphe
Finally inserts into hyoid bone
Mylohyoid function
Hyoid fixed: jaw opening
Hyoid not fixed: raise hyoid and FOM
innervation of mylohyoid
Vc motor root - nerve to mylohyoid (branch of IAN)
Anterior belly of diagnostic origin and insertion
Origin: digastric fossa
insertion: intermediate tendon (—> posterior belly)
Anterior belly of digastric action
Hyoid fixed: jaw opening
Hyoid not fixed: raise hyoid
Innervation of ABD
Vc motor root - via nerve to mylohyoid (branch of IAN)
What are the hyoid stabilisers (5)?
- Sternohyoid
- Omohyoid
- Thyrohyoid
- PBD
- Stylohyoid
What is the function of the hyoid stabilisers?
Simultaneous contraction of these muscles will stabilise the hyoid bone, allowing the other muscles to act as depressor muscles.
Plane line articulator
Hinge axis may be more anatomical but arbitrary. The simpliest type of articulator consisting of a simple hinge joint. No lateral or sliding movements are possible with a plane line articulator.
Average value articulator
Provide lateral excursive and protrusive movements and have condylar inclinations set to an average value of 30°.
Simple fixed prosthetics for teeth not involved in guidance/removable prosthetics.
Denatus articulator
Non-arcon (condyle part of maxillary component)
Denar Mark II articulator
Arcon (condyle part of mandibular component)
Facebow
- Relates maxillary cast to inter-condylar axis but uses ear as a reference.
- Orientation of cast in vertical dimension governed by a marker relating to the lateral incisor
What informs the articulators condylar guidance angles?
At least two interocclusal records
1. Retruded contact position
2. Plus relevant excursions
What can Denar Mark II Arcon articulators be used for?
it can be used for more advanced restorative work such as bridges, implants , orthodontic repositioning
